Numerical classification of the coastal vegetation of Attu Island, Aleutian Islands, Alaska

Abstract

Abstract. This phytosociological study of the beaches, dunes, and associated lower mountain slopes of Attu Island is the first effort to identify the major coastal vegetation types of the Aleutian Islands using numerical methods. It is the first attempt to use the relevé method in southern coastal Alaska and provides a basis for future comparison with other areas. 76 relevés represent the range of structural and compositional variation in the matrix of vegetation and landform zonation at 16 locations. Data are analyzed by multivariate methods using the MULVA‐4 computer package and ordered with Wildi's numerical procedure to produce results similar to traditional phytosociological tabular classification. Nine major community types are distinguished in four physiognomic groups: 1. Dwarf‐shrub mire: Vaccinium uliginosum‐Empetrum nigrum; 2. Meadow: Athyrium filix‐femina‐Streptopus amplexifolius, Artemisia tilesii‐Veratrum album, Elymus mollis‐Montia (Claytonia) sibirica, Ligusticum scoticum‐Elymus mollis; 3. Beach meadow: Elymus mollis‐Senecio pseudo‐arnica, Lathyrus maritimus‐Elymus mollis; and 4. Beach: Mertensia maritima and Arenaria (Honckenya) peploides. These community types are described and interpreted in response to a complex, topographic gradient. Phytogeographic comparison of Attu Island with neighboring areas suggests close relationship to the beach and beach‐meadow types of eastern Kamchatka and to the mesic meadows of the Alaskan Semidi Islands; there is a slightly lower relationship to the mesic meadows of nearby Buldir Island.